The present invention relates to a steering assembly supporting device of a motor vehicle.
The body of a motor vehicle normally comprises cowl side panels extending forward from the front ends of corresponding front door opening flanges, a cowl inner panel arranged to extend between the cowl side panels at a position beneath a wind shield, and a dash panel separating a driver's compartment from an engine compartment. In addition, in a motor vehicle, the tip of a steering tube passes through the dash panel and extends to the inside of the engine compartment. In such a motor vehicle, the steering tube, used to support a steering shaft, is normally supported in such a way that the intermediate portion of the steering tube is fixed onto both the cowl inner panel and the dash panel via a steering support and that the steering tube is fixed onto the dash panel at a position wherein the steering tube passes through the dash panel. However, in the case wherein the steering tube is supported as mentioned above, since the distance between the rear end of the steering support, which supports the steering tube and the front end of the steering support, at which site the steering support is fixed onto the cowl inner panel, is very long, when a motor vehicle is driven at a high speed or on a rough load, a problem occurs in that the steering wheel vibrates.
Swedish Patent publication No. 406303 discloses a steering assembly supporting device which comprises a steering assembly supporting member extending in parallel to and spaced from the cowl inner panel. The opposite ends of the steering assembly supporting member are fixed into the corresponding cowl side panels, and the steering assembly is supported by the intermediate portion of the steering assembly supporting member. This steering assembly supporting member has a hollow tubular construction over the entire length thereof and comprises U-shaped cross-sectional member and a flat member which are welded to each other. In addition, this steering assembly supporting member is so formed that the central portion thereof has a large cross-section and the opposite end portions thereof have a small cross-section, and the steering assembly is supported by one of the opposite end portions of the steering assembly supporting member. However, in this prior art, since the steerng assembly supporting member is formed so as to extend between the cowl side panels, the length of the steering assembly supporting member is very long. Consequently, in the case wherein the steering assembly supporting member is formed over the entire length thereof by the U-shaped cross-sectional member and the flat member which are welded to each other as mentioned above, since a high degree of accuracy is required regarding the size of the U-shaped cross-sectional member and the flat member, a problem occurs in that the manufacturing cost of the steering assembly supporting member is increased. In addition, in the case wherein the steering assembly supporting member has a welding construction over the entire length thereof, another problem occurs in that the steering assembly supporting member will be heavy. On the other hand, the rigidity of the steering assembly supporting member portion which is located between the steering assembly and the cowl side panel which is located near the steering assembly has a great influence on vibration of the steering assembly supporting member. However, in the above-mentioned prior art, the above-mentioned steering assembly supporting member portion has a small cross-section as mentioned above and, thus, since the degree of rigidity of the steering assembly supporting member portion is small, a problem occurs in that the steering wheel will vibrate when a motor vehicle is driven at a high speed or on a rough load.
In addition, German laid open Patent publication No. 2746183 discloses a steering assembly supporting device in which the steering assembly supporting member is formed by a hollow tube. In the case wherein the steering assembly supporting member is formed by a hollow tube as mentioned above, there is an advantage in that the weight of the steering assembly supporting member is reduced. However, in this case, since the degree of rigidity of the steering assembly supporting member is small, a problem occurs in that the steering wheel will vibrate when a motor vehicle is driven at a high speed or on a rough load. If the cross-sectional area of the hollow tube is increased, it is possible to prevent the steering assembly supporting member from vibrating. However, if the cross-sectional area of the hollow tube is increased, the weight of the steering assembly supporting member is increased, and the size of the driver's compartment is reduced. Consequently, it is genuinely difficult to increase the cross-sectional area of the hollow tube.